Hinge axis locator



Dec. 20, 1955 v CLARK 2,727,307

HINGE AXIS LOCATOR Filed Oct. 10, 1952 INVEN TOR. EOI'V/A/ 540a? 6012K/S ATTOE/VEKS 2,727 ,307 ent d Pia;- $9. 355

HINGE LOCATOR Edwin Bruce Clark, Pittsburgh, Pa., assignor to CresentDental Manufacturing Company, Chicago, Ill.

Application October 10, 1952, Serial No. 314,083 9 Claims. (Cl. 32-20)This invention relates to a dental appliance to be used in locating thehinge axis of the human lower jaw.

In certain types of restorative dentistry it is necessary to locateaccurately the true hinge axis of the lower jaw. This axis, in extactrelation to the patients bite, must be transferred to an articulatorhaving parts that simulate the action of the patients jaw so that thedentist can build a replica of the patients bite in the articulator.

Devices have previously been proposed to locate this hinge axis, butthese devices have been heavy and cumbersome and have requiredconsiderable time to locate the hinge axis accurately. Because of theircomplicated nature, involving many mechanical parts made to ver,accurate dimensions, they have been expensive.

The present invention provides a hinge axis locator that is simple andinexpensive, of light-weight construction, and which can be easily andquickly manipulated to locate the hinge axis of the lower jaw.

Further objects and advantages of the invention will become apparent asthe description proceeds.

In the drawings:

Fig. l is a perspective view of the hinge axis locator attached to adental tray.

Fig. 2 is a side elevation of the device shown in Fig. 1.

Construction In a preferred form of the invention, as shown in thedrawings, a stud 10 is soldered or otherwise secured to the impressiontray 11, which is otherwise of usual construction. The stud 10 has athreaded socket into which fits a threaded end formed on stem 12.

A cross bar 13 is secured by a universal clamp 14 to stem 12, the clampbeing movable both rotatably and slidably on the stem 12.

A side arm 15 is attached to each end of the cross bar by a screw threador any other preferred connection. As shown in the drawings, these armslie in a single plane and are parallel to each other. The cross bar 13and side arms 15 may, of course, be formed from a single piece ofmaterial if preferred.

The outer end of each side arm 15 is drilled to accommodate an axispointer 16, and a set screw 17 holds each pointer in place. The twopointers 16 project inwardly on a common axis at right angles to theside arms 15. Each pointer has a heavy base portion engaged by set screw17, and a thin, needle-like extension 18. The pointers are formed ofsome suitable material that is dead soft, without appreciableresilience, so that they will stay in any position to which they may bepushed without springing back to any appreciable extent. For example,the pointers may be formed of 24 carat gold, in which case they shouldbe annealed before each use, to insure their being in dead softcondition.

It is advantageous to have the device as light in weight as possible,and therefore all of the parts are preferably made of some strong yetlight-weight material such as an alloy of aluminum or magnesium. But insome cases it may be desirable to form some of the parts, such as theuniversal clamp 14 and the screws 17 from ferrous metal.

Since the hinge axis locator of'the p'res en'tinveiition contains fewand simple parts, when they are made of light-weight material the deviceis ofiextreinely light weight. Because of this light weight if ispossible to use an ordinary impression tray and ordinary imp ionmaterial to attach the device to the patients'lowerjah/I" With theheavy, cumbersome devices of'the prionart it has been necessary to usespecial castings to attach are axis locator to the patientsjaw."

Additional advantages of light weight are that lightness adds to thepatieints comfort and assists in obta ing' a quick and accurate reading,since itis'easier for epatient torelaxhisjawmuscles.

Operation In using the hinge axis locator the device is separated fromthe impression tray 11; The tray 11 is first fille'd with suitableimpression material and 'is'applie'd," th position indicated in Fig. 2,over the teeth of the' lower jaw of the patient -When the impressionmaterial sets it forms a sufliciently strong attachment of the tray'tothe jaw to permit carrying out the following operations.

The stem 12 is now secured to the tray by screwing its end into thethreaded socket of the stud 10, and the frame of the locator is attachedto the stem 12 by means of the universal clamp 14.

The human lower jaw, in opening, first rotates on a hinge axis until thejaw has opened about one-half of an inch, after which the jaw can slideforward away from the axis. It is the function of the device of thepresent invention to locate accurately this hinge axis.

When the dentist first applys the apparatus to the stem 12 he moves theframe in the universal clamp 14 until the axis pointers 16 pointapproximately at the hinge axis. He then tightens clamp 14, and the arms15 will be ap proximately in the position illustrated in Fig. 2. Theclamp 14 therefore serves as a coarse adjustment of the device.

The dentist now assists the patient in opening and closing his jaw onthe hinge axis. As he locates this axis, the dentist moves the softprojecting ends 18 of the pointers 16 until their inner ends cease tomove, at which time they point exactly at the hinge axis of the loweraw.

Due to the fact that they are formed of dead soft material, withoutappreciable resilience, the ends 18 of the pointers do not spring back,but remain in the position to which they are pushed by light fingerpressure. The pointers 16 can therefore be brought very quickly andeasily to a position in which they point accurately at the hinge axis.The pointers 16 thus serve as a fine adjustment for the hinge axislocator.

After the hinge axis has been located the device is removed from thepatient without bending the pointers 16. The axis, thus located, can nowbe transferred to an articulator to assist the dentist in building areplica of the patients bite in the articulator. Or, if preferred, inkspots can be placed on the cheeks of the patient, and the axis thuslocated can be transferred by means of a transfer face bow.

The device of the present invention provides a hinge axis locator thathas a low first cost and low operating costs. It is convenient for bothpatient and dentist, and locates the hinge axis in a minimum amount oftime.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. A hinge axis locator comprising: an-impression tray having a studsecured thereto, a stem detachably connected to the stud, a framesecured to the stem by a universal clamp, the frame including a crossbar and two side arms,

and an axis pointer carried by each side arm, the axis pointersprojecting inwardly along a common axis, and being formed of dead softbendable material.

2. A device as recited in claim 1 in which the axis pointers are formedof gold, of a fineness of approximately 24 carat.

"3. A device as recited in claim 1 in which the stem, frame anduniversal clamp are formed of light-weight material.

4.,A hinge axis locator comprising: a stem adapted to be rigidlyattached to the lowerjaw of a patient, a frame secured to the stem by anadjustable connection which forms a coarse adjustment, and a pair ofaxis pointerscarried by the frame, the axis pointers projecting inwardlyalong a common axis, and being formed of dead soft bendable material toform a fine adjustment to'locate the hinge axis of the lower jaw.

; 5. A deviceas claimed in claim 4 in which the axis pointers, areformed of gold, of a fineness of approximately 24 carat.

6. A device as claimed in claim 4 in which the stem and the frame areformed of light-weight material. 7. A hinge axis locator comprising: animpression tray of the usual type adapted to be secured over the teethof a lower jaw by the usual impression material, a

the impression tray carrying a stud which projects over the chin of thepatient, a stem detachably connected to the stud, a universal clampattached to the stem and serving as a coarse adjustment in locating theaxis, a frame attached to the clamp, the frame having two side armswhich extend in the same plane, an axis pointer detachably connected tothe outer end of each side arm, the axis pointers projecting inwardlyalong 'a common axis, and being formed of dead soft bendable material toform a fine adjustment to locate the hinge axis of the lower jaw.

8. A device as recited in claim 7 in which the axis pointers are formedof gold, of a fineness of approximately 24 carat. H

9. A device as recited in claim 7 in which the stem, universal clamp andframe are formed of light-weight metal.

References Cited in the file of this patent UNITED STATES PATENTS2,579,111 Fleischhacker Dec. 18, 1951

